Method of treating hydrocarbons



United States Patent 3,039,954 METHGD OF TREATING HYDROCARBONS Michael D. Riordan, Fishkill, and William F. Franz, Beacon, N.Y., assignors to Texaco Inc, a corporation of Delaware No Drawing. Filed Dec. 27, 1956, Ser. No. 630,733 4 Claims. (61. 208-65) This invention relates to a method of treating hydrocarbons and more particularly to the production of high octane motor fuels.

Currently, one of the most popular refining methods for the production of high octane motor fuel is to subject a naphtha fraction to reforming conditions. Reforming is the term used to describe the treatment of a mixture of hydrocarbons in which at least some of the hydrocarbons undergo molecular rearrangement such as isomerization and cyclization accompanied by hydrogenation, dehydrogenation and aromatization. The reforming may be performed either in the presence or absence of a catalyst although most of the commercially successful reforming processes are conducted in the presence of a catalyst and added hydrogen.

One of the most commercially successful reforming catalysts is the platinum type catalyst which generally recently, fuels in this octane range have satisfactorily the life of the platinum catalyst as to render such conditions economically impractical. When operating under conditions necessary to produce a fuel having a leaded research octane number of at least 100, it has been found that the life of the platinum catalyst is approximately /3 of that when the reforming operation is conducted under the less severe conditions necessary for the production of a fuel having a leaded research octane number in the 90-98 range. The short life of the reforming catalyst under such severe operating conditions thus renders the use of a platinum reforming catalyst economically impractical for the production of 100+ octane fuel.

We have now discovered a method for the production of motor fuels having leaded octane numbers in excess of 100. According to our invention the hydrocarbons intended for use as a motor fuel are subjected to the.

action of a zinc oxide-zinc chromite catalyst at elevated temperatures. In a specific embodiment of our invention a reformate which has been produced by the catalytic reforming of a straight run naphtha under mild operating conditions is subjected to the action of a zinc oxidezinc chromite catalyst.

One of the particular advantages'of the zinc oxidezinc chromite catalyst is its ease of regeneration. Another advantage is its resistance to heat. The catalyst may be regenerated simply by burning off the deposited carbon. During regeneration, temperatures as high as 1600 F. have been reached and apparently have no ill effect on the activity of the catalyst. The catalyst has also been regenerated as many as 40 times Without suffering any loss in activity.

In contradistinction, the life of the platinum reforming catalyst is considerably curtailed by high temperaice tures. In addition, platinum catalysts of the non-regenerable type must be reprocessed once they have become spent, the reprocessing amounting to recovery of the platinum from the spent catalyst and the formulation of the recovered platinum into fresh catalyst. Because of the high initial investment for the platinum catalyst and the high cost of reprocessing, economic considerations make it mandatory to operate the reforming catalyst under as mild conditions as possible to preserve the catalyst life. The situation then is somewhat of a paradox since industry is requiring 100+ octane fuels yet the cost of producing such fuels by the most advantageous refining process currently known is prohibitive. Now, however when the zinc oxide-Zinc chromite catalyst is used for the after-treatment of a stock which has been reformed under mild conditions, it is possible to produce fuels having octane numbers Well in excess of 100.

The catalyst employed in the present invention comprises two components, namely zinc oxide and Zinc chromite, the zinc chromite being present in an amount between 10 and 90% by weight based on the combined weights of the zinc oxide and zinc chromite and preferably between 25 and The Zinc oxide-zinc chromite catalyst may be used alone or may be supported on a substantially inert base. The catalyst may be prepared in the following manner.

Solution No. 1.3036 grams of GP. ammonium dichromate were dissolved in ten liters of water. A solution of 2400 ml. concentrated ammonium hydroxide in four liters of water was added. 7

Solution N0. 2.7134 grams of CPZn(NO .6H O were dissolved in 16 liters of water.

Solutions 1 and 2 were then mixed by being added slowly and simultaneously at equal rates with good agitation to a vessel containing four liters of water. Stirring was continued for one-half hour after the addition was complete. 600 ml. concentrated ammonium hydroxide were then added to ensure complete precipitation.

The precipitate was filtered and washed three times with ten liters of water. After having been dried, the resulting powder was decomposed in small portions by heating to incipient decomposition temperature. The decomposition temperature was found to be about 640 F. The powder was then sieved through 20 mesh, pelletted in dies with 2% Sterotex and calcined at 750 F. for 12 hours. 2850 grams or 2240 cc. of dark brown pellets were obtained. When the catalyst is intended for use in a fluidized system, the decomposed powder is ground to a particle size of less than 200 microns in diameter with a major proportion between 20 and lTllCIOIlS.

The resulting catalyst contained 26% ZnO and 74% ZnCr O by weight. The composition of the catalyst may be varied by using appropriate amounts of ammonium dichromate and zinc nitrate as the starting materials. The catalyst may also be prepared by other methods known to those skilled in the art.

Although the process of the invention is applicable to many hydrocarbon-containing feed stocks, a preferred feed for the zinc oxide-Zinc chromite catalyst is a catalytic reformate which has been produced under mild reforming conditions. The entire liquid product of the catalytic reforming reactor or a selected portion thereof may form the feed stock for the zinc oxide-zinc chromite reactor. It is also possible to pass the entire effluent from the reforming reactor to the zinc oxide-zinc chromite reactor without separating the normally liquid components from the normally gaseous components of the reformer efiluent.

The space velocity, that is the volume of feed per volume of catalyst per hour employed in the zinc oxidezinc chromite reactor is preferably 0.2-4 although space velocities of from 01-10 may be used. Of course, when the entire efiiuent from the reforming reactor is passed to the zinc oxide-zinc chromite reactor the space velocity is based on the normally liquid component of the effluent and not on the entire effluent. Temperatures in the zinc oxide-zinc chromite reactor may range from 900-1200 F. although temperatures of 925-1100 F. are preferred. Hydrogen rates may range from 500-10,000 cu. ft. per bbl. of feed. Pressures ranging from -1000 p.s.i.g. or higher may be used although pressures of 250-750 p.s.i.g. are preferred.

In order to illustrate our invention, the following examples are given.

EXAMPLE I A 91 octane reformate prepared by treating a straight run naphtha fraction with a platinum on alumina catalyst under relatively mild conditions was passed over a zinc oxide-Zinc chromite catalyst, prepared as described above, at temperatures of 950, 975 and 1000 F., a space velocity of 1.0 v./v./hr., 500 p.s.i.g. H pressure and a gas recycle rate of 9,169 cu. ft. per bbl. The following results were This example illustrates a two stage integrated process for the production of 100+ octane fuel. A straight run naphtha fraction having an ASTM distillation range of 174-372 F., a hydrocarbon analysis of 42% parafiins, 42% naphthenes and 16% aromatics, an ASTM research octane number clear 52.8, leaded 73.1 was used to evaiuate a platinum-on-alumina reforming catalyst. It was determined. that at an average operating temperature of 925 F., a pressure of 500 p.s.i.g., a space velocity of 3.0 and a recycle rate of 8000 cu. ft. per bbl., a product having an AST M research octane clear of 91.3, leaded 98.6, was obtained in 82.4 volume percent yield of 0 hydrocarbons. After these conditions had been standardized a two stage process was inaugurated in which the entire efliuent from the reforming reactor operated under the above conditions was passed into a reactor containing a zinc oxide-zinc chromite catalyst composed of 26% zinc oxide and 74% zinc chromite. The pressure in the zinc oxide-zinc chromite reactor was maintained at 500 p.s.i.g., the space velocity at 1.0 v./v./hr. and the temperature at approximately 975 F. The product gas recovered from the efiiuent of the zinc oxide-zinc chomite reactor was recycled to the reforming reactor at the rate of 8000 cu. ft./ bbl. :Table 11 below sets forth the results obtained after 11 hours of operation. Table III shows the results obtained after 90 hours of continuous operation.

Table 11 Wt. percent recovery C 79.3 Hydrocarbon analysis:

Percent aromatics 66 Percent olefins 2 Percent saturates 32 AS'IM research octane No.:

Clear 99.6 +3 cc. TEL/gal 104.16

1 Wiese scale.

4 Table III Wt. percent recovery 76.6 Hydrocarbon analysis:

Percent aromatics 68 Percent olefms 4 Percent saturates 28 ASTM research octane No.:

Clear 99.5 +3 cc. TEL/gal 104.16

1 Wiese scale.

The activity of the zinc oxide-zinc chromite catalyst is not limited to the upgrading of motor fuels having octane numbers in the 90s. The catalyst is equally etfective in upgrading starting materials which have an octane number in excess of 100 as is shown in the following example.

EXAMPLE III A reformate was passed over a zinc oxide-zinc chromite on alumina catalyst containing 5.2 wt. percent zinc oxide, 14.8 wt. percent zinc chromite and wt. percent alumina at various temperatures and space velocities, 500 p.s.i.g. hydrogen pressure, a gas recycle rate of 8000 cu. ft. per bbl. and a fresh hydrogen input of 1272 cu. ft. per

bbl. The results obtained are set forth below in Table IV.

Table IV Temperature, F 1, 000 1, 025 1, 100 Space Velocity v./v./hr 0.5 0.5 1. 0 Time on stream, Hrs 12 24 60 Vol. Percent Recovered 0 87.9 86.2 85. 5 Wt. Percent Recovered 05+ 88.0 87.5 87. 5

Charge ASTM Distillation:

IB 222 139 10 280 259 not not 50.--- 310 300 availavail- 346 348 able able EP 382 406 ASTM Research Octan 1 Clear 101. 4 106. 47 107. 15 107. 15 +3 00. TEL/gal 103.7 110. 74 111.36 110. 53

1 Wiese scale.

One of the particular advantages of the present process is the fact that the catalyst is easily regenerable and is quite resistant to heat.

EXAMPLE IV A used zinc oxide-zinc chromite catalyst was regenerated by burning oif the carbon accumulation. During the regeneration, a maximum temperature of 1600 F. was reached. A 91 octane reformate was then passed over the regenerated catalyst at various temperatures, a space velocity of 1.0 v./v./h., 500 p.s.i.g. and a gas recycle rate at 8000 cu. ft. per bbl. The results obtained are set forth in Table V. e

l Wiese scale.

A comparison of the data in Table V with that of Table I shows that the regeneration restored the catalyst to its original activity. 7

In the case of the integrated two stage process shown in Example H, it may be desirable in some instances hefore recycling the product gas to the catalytic reformer to so treat the gas as to increase the hydrogen content of the gas or to prevent the buildup of impurities therein.

Obviously, various modifications may be made in the foregoing disclosure without departing from the spirit of the invention.

We claim:

1. A process for the production of a high octane motor fuel which comprises subjecting a straight run naphtha fraction to the action of a reforming catalyst in a reforming Zone under reforming conditions to produce a reformate having a clear research octane number of at least 80, passing the entire efiiuent from said reforming zone into contact with a catalyst comprising Zinc oxide and zinc chromite, at a temperature between 900 and 1200 F., a pressure between and 1000 p.s.i.g. and a space velocity between 0.1 and 10, said zinc oxide-zinc chromite catalyst containing between and 90% zinc oxide based on the combined weights of zinc oxide and zinc chromite, separating the efiluent from the zinc oxidezinc chromite catalyst reaction zone into normally gaseous components and normally liquid components and re- 4. The process of claim 3 in which the zinc oxide-zinc chromite catalyst contains between and zinc oxide based on the combined weights of zinc oxide and zinc chromite.

References Cited in the file of this patent UNITED STATES PATENTS 1,746,782 Lazier Feb. 11, 1930 2,205,141 Heard June 18, 1940 2,209,458 Heard et al. June 30, 1940 2,378,209 Fuller et al June 12, 1945 2,418,888 Kearby Apr. 15, 1947 2,758,062 Arundale et a1. Aug. 7, 1956 2,960,460 Ryer et a1. Nov. 15, 1960 

1. A PROCESS FOR THE PRODUCTION OF A HIGH OCTANE MOTOR FUEL WHICH COMPRISES SUBJECTING A STRAIGHT RUN NAPHTHA FRACTION TO THE ACTION OF A REFORMING CATALYST IN A REFORMING ZONE UNDER REFORMING CONDITIONS TO PRODUCE A REFORMATE HAVING A CLEAR RESEARCH OCTANE NUMBER OF AT LEAST 80, PASSING THE ENTIRE EFFLUENT FROM SAID REFORMING ZONE INTO CONTACT WITH A CATALYST COMPRISING ZINC OXIDE AND ZINC CHROMITE, AT A TEMPERATURE BETWEEN 900 AND 1200*F., A PRESSURE BETWEEN 0 AND 1000 P.S.I.G. AND A SPACE VELOCITY BETWEEN 0.1 AND 10, SAID ZINC OXIDE-ZINC CHROMITE CATALYST CONTAINING BETWEEN 10 AND 90% ZINC OXIDE BASED ON THE COMBINED WEIGHTS OF ZINC OXIDE AND ZINC CHROMITE, SEPARATING THE EFFLUENT FROM THE ZINC OXIDEZINC CHROMITE CATALYST REACTION ZONE INTO NORMALLY GASEOUS COMPONENTS AND NORMALLY LIQUID COMPONENTS AND RECYCLING AT LEAST A PORTION OF SAID NORMALLY GASEOUS COMPONENTS TO SAID REFORMING ZONE. 